The present invention relates to an external auxiliary magnetic storage device, and in particular, to a magnetic storage device using a small sized disk.
The development of lightweight, portable, low power consuming computers and peripherals has resulted in greater advances in miniaturization of hard disk devices. The disk diameter has been reduced from 14 inches, to 8 inches, to 5.25 inches and even as small as 3.5 inches. The miniaturization of disk diameters requires a corresponding increase in disk storage density and track density as well as driving systems for tracking such disks.
Conventional micro-hard disk driving systems are known from U.S. Pat. No. 4,568,988 which provides a disk drive system compatible with 3.5 inch disks. A rotary actuator is coupled to a step motor by a steel belt so that the rotation of the step motor causes movement of the rotary actuator. However, this is an open loop system which does not achieve positioning control with respect to the recording track on the disk surface. Accordingly, the tracking head positioning error tends to increase. Additionally, such a system does not lend itself to the decreasing of track density. The two phase of the step motor are uniformly excited and therefore, the device becomes restricted in the number of tracks which can be traversed by the head due to the step angle of the step motor and the structure of the steel belt.
A method and apparatus for recording and detecting information while decreasing track density which is utilized in storage devices operating on large size 14 inch and 8 inch disks is known from U.S. Pat. No. 3,534,344. This method is known as the dedicated surface servo method in which data for head positioning is recorded on one surface, the servo surface, of the disk. Control of the voice coil motor is performed based upon the stored positioning data so that a positioning scheme for the actuator is provided. However, in this method, because one surface of the disk is utilized for servo data, it can not be used for normal data storage, reducing the storage capacity and efficiency for the device. This problem is amplified in small sized devices which utilize only one or two disks. Additionally, the control circuit becomes more complicated increasing the cost of the overall device.
A method for solving the position detection problem for a track following a servo system utilizing a sector servo system is known from U.S. Pat. No. 3,593,333. Each sector is a divided unit of data provided within each disk track. Each sector normally has a storage capacity of 256, 512, or 1024 bytes. Therefore, there are ten to several tens of sectors within one track. A servo region containing the servo data is provided in the leading edge and a trailing edge of each sector so that positioning control is performed in each sector and a special servo surface is no longer needed reducing the useless portion of the disk recording surface. However, in this system, it is required that there be a method for detecting the servo region accompanying each sector and since each servo region corresponds to a respective sector, it is impossible to change the size and number of sectors after shipment of this device, i.e. once these sectors have been determined.
A data transducer position control system for rotating disk data storage equipment utilizing a wedge servo region or index servo system so that the servo region for positioning is provided at one portion in each track of the disk surface is known from U.S. Pat. No. RE. 32075. This method performs head positioning correction each rotation of the disk. A predetermined timing region acts as the servo region based upon an index signal which is generated once each rotation of the disk. The size of this sector is no longer restricted as in the previous sector servo system, a complicated control system is no longer required and the working efficiency due to useless recording surfaces is no longer a problem as was in the dedicated servo system. However, due to the fact that only one correction occurs per rotation, the head position can not be amended where the eccentricity of the disk changes over time and as the disk rotates the change occurs in a non-repeating manner. For example, in the case of the development of the eccentricity after shipment in which the head deviates towards the outer region of the disk in one portion of the circumference but will deviate inwardly on the opposite side. Accordingly, it is impossible to prevent such error by correcting the head only once per each rotation.
Accordingly, a position control system for a magnetic storage device using a small sized disk which overcomes the shortcomings of the prior art is desired.